<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
</head>
<body>

</body>
</html>
<script>
    function Fun(x) {
        return function(y) {
            console.log(x+y);
        }
    }

    var obj = Fun(4);
    // 相当于  obj = function() {console.log(x)}
    obj();
    obj(2);
</script>